The prior art has recognized the potential of peat moss material for use as an absorbent medium in structures for absorbing body exudate. Peat moss material has highly desirable fluid absorption properties such as a remarkable absorption capacity and the ability of "drying" adjacent materials by continuing to pull or wick fluid away from them over a long time period such that virtually all the fluid is collected in the peat moss core. These attributes allow the material to provide highly efficient absorbent components which can be made relatively thin for better fit, comfort and discretion, while being sufficiently absorbent to prevent overflow leakage and garment staining.
The following United States Patents document the use of peat moss material for manufacturing absorbent components for disposable absorbent products:
______________________________________ U.S. Pat. No. INVENTOR DATE ISSUED ______________________________________ 4,170,515 Lalancette et al. October 9, 1979 4,215,692 Levesque August 5, 1980 4,226,237 Levesque October 7, 1980 4,305,393 Nguyen December 15, 1981 4,473,440 Ovans September 25, 1984 4,507,122 Levesque March 26, 1985 4,618,496 Brasseur October 21, 1986 4,676,871 Cadieux et al. June 30, 1987 4,992,324 Dube February 12, 1991 5,053,029 Yang October 1, 1991 ______________________________________
The subject matter of these references is incorporated herein by reference.
Peat moss material can be formed in a highly cohesive board by any one of the methods disclosed in the above identified prior art. In a board form, the peat moss material is convenient to handle and it can be directly processed in high speed automatic equipment for assembling disposable absorbent products.
More particularly, the method for producing the peat moss board consists of classifying raw peat moos material in particulate form to retain only the particles which are the most absorbent. The screened fraction is sheeted on a Fourdrinier wire in the form of a slurry and dewatered by the application of vacuum. The thus formed board is dried and calendered to increase its density to the desired level. In order to tenderize, soften and improve the flexibility of the calendered peat moss board, it may be subjected to mechanical working such as perf-embossing and micro-corrugating as described in the U.S. Pat. Nos. 4,559,050 and 4,596,567 to Iskra, issued on Dec. 17, 1985 and Jun. 24, 1986 respectively. The disclosure of these patents is incorporated herein by reference.
It is known in the art to classify peat moss material by forming an aqueous slurry of peat moss having a pumpable consistency and flowing the slurry on successive screens of increasing mesh size to eliminate from the slurry the fines and then the excessively large particles such as roots and branches. A major drawback of currently practised wet classification processes resides in the incomplete elimination of the fines from the slurry by the straining action of the screens. The cause of this problem is twofold. Firstly, the fines have the ability to adhere to coarser peat moss fragments which carry the fines through the various screening stages and into the final product. Secondly, the screen openings have a tendency to rapidly become clogged by fines and small fibers. As a result the screen becomes partially or totally inoperative.
Another drawback of prior art wet classification processes is the loss of a certain quantity of small absorbent particles from the slurry which have a tendency to adhere to oversize fragments in the slurry and are extracted and discarded with the oversize fragments during the screening stages. As a result, the peat moss raw material is utilized less efficiently which increases the manufacturing costs of the absorbent product.